diff --git a/src/openvpn/ssl_mbedtls.c b/src/openvpn/ssl_mbedtls.c
index 8e31980..ef83e65 100644
--- a/src/openvpn/ssl_mbedtls.c
+++ b/src/openvpn/ssl_mbedtls.c
@@ -853,7 +853,7 @@ tls_ctx_personalise_random(struct tls_root_ctx *ctx)
         const md_kt_t *sha256_kt = md_kt_get("SHA256");
         mbedtls_x509_crt *cert = ctx->crt_chain;
 
-        if (0 != md_full(sha256_kt, cert->tbs.p, cert->tbs.len, sha256_hash))
+        if (!md_full(sha256_kt, cert->tbs.p, cert->tbs.len, sha256_hash))
         {
             msg(M_WARN, "WARNING: failed to personalise random");
         }